Facing the prospect of a second wave of coronavirus cases, China announced plans Monday to rapidly test all 11 million residents of Wuhan, the original epicenter of the pandemic, in just 10 days, according to internal government documents. Confusion ensued over the next couple days: Was a 10-day plan feasible, and if so, when would it start? An employee on a hotline set up by Wuhan’s mayor clarified to the New York Times that the plan was a directive to the city’s individual districts: Some would start earlier than others, but each would test its residents within 10 days. But now that mass testing has begun, questions remain about how the swift implementation and unprecedented scale are possible and whether such aggressive measures are necessary.

The campaign—what a government notice is calling “10 days of battle”—began after Wuhan reported a small cluster outbreak of six cases over the weekend, after going more than a month without new infections. All six came from the same residential compound, and five were asymptomatic. (The housing manager of the complex has since been removed.) Wuhan has been held up in China as an example of the country’s success in responding to the pandemic, but the cases immediately sparked fears of asymptomatic transmission in Wuhan, whose 76-day lockdown ended April 8.

At least seven neighborhoods said they would begin testing Wednesday, and residents have already started waiting in hourlong lines for tests, Reuters reported. The tests are free, and residents say they seem voluntary. They’re being advertised through flyers, loudspeaker announcements, and social media. And while authorities have said they intend to test all 11 million Wuhan residents, they’re prioritizing individuals from 12 high-risk categories, including students, medical and supermarket workers, and travelers. The government has also said it will target residential compounds with older people and densely populated neighborhoods, according to the Times.

It’s still unclear how China plans to procure and process all the testing kits. Third-party companies are scrambling to meet demand, and testing labs have started shipping equipment from other cities, but last month Wuhan’s deputy mayor, Li Qiang,said that Wuhan could test about 46,000 individuals per day. Health News, the official newspaper of the Chinese medical system, said on Tuesday that Wuhan currently has a testing capacity of only 100,000 people per day, Reuters reported.

There’s also been confusion over how residents will be tested. Third-party companies and some hospital employees are performing the tests, but one neighborhood official told Caixin magazine that he wasn’t sure if he should send his residents to the hospital or ask doctors to establish a testing center in the neighborhood, the Times reported. And while some notices refer to all residents, others exempt children under 6.

But the aggressive testing plan clearly has advantages—namely, it’s a way for Wuhan authorities to try to avoid another strict lockdown and to mitigate fear.

Still, the program, which will cost the city an estimated 1 billion yuan (about U.S.$141 million), isn’t universally favored. Wuhan residents have expressedconcerns about infection in long testing lines, and some wonder whether such drastic, time-consuming, and expensive measures are necessary when infection rates are so low. Even Dr. Wu Zunyou, the chief epidemiologist of China’s Center for Disease Control and Prevention, said on state television Tuesday that testing should be tailored to “key areas and key groups,” according to the Times. “In communities without infections, there is no need to screen everyone,” Wu said.

At this point it’s hard to tell whether testing at this scale in Wuhan is necessary—and to what extent it might be helpful in stemming a second wave of COVID-19. But it does put into starker relief the shortages in the U.S., where testing continues to fall short of what scientists recommend. While China is debating the merits of mass testing in cities with a handful of new cases, the U.S. is seeing tens of thousands of confirmed cases each day, while President Donald Trump calls testing “overrated,” despite being the recipient of a daily test himself.